This invention relates generally to the field of disc drive data storage devices, and more particularly, but not by way of limitation, to a system for mounting head/head suspension assemblies to actuator arms in a disc drive.
Disc drives of the type referred to as xe2x80x9cWinchesterxe2x80x9d disc drives, or hard disc drives, are well known in the industry. Such disc drives record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speed of up to 10,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning disc to fly the head assembly in a closely spaced relationship to the disc surface.
In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by head suspensions, or flexures.
A typical head suspension includes four integrally formed portions: 1) a mounting portion, for attaching the head suspension to the actuator used to move the heads from track to track; 2) a spring portion, to provide a counterbalancing force to balance the hydrodynamic lifting force of the slider and to maintain consistent flying height of the head; 3) a rigid beam portion for transferring the counterbalancing force of the spring portion to the head assembly; and 4) a gimbal portion, to which the head assembly is attached, which is compliant in the head assembly""s roll and pitch axes to allow the slider to follow minor variations in the flatness of the discs, and stiff in the head assembly""s yaw and in-plane axes, to permit accurate positioning of the head relative to the data tracks.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. An actuator bearing housing is mounted to the pivot shaft by an arrangement of precision ball bearing assemblies, and supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member. On the side of the actuator bearing housing opposite to the coil, the actuator bearing housing also typically includes a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and heads, in accordance with the well-known Lorentz relationship. As the actuator bearing housing rotates, the heads are moved radially across the data tracks along an arcuate path.
The head suspensions described above are typically fabricated from full hardened 300 series stainless steel foil, with flexures of the current generation being formed from flat stainless steel stock 0.0025 inches thick. A typical head suspension which could be modified in conformance with the present invention is described in detail in U.S. Pat. Nos. 5,428,490 and 5,331,489, both assigned to the assignee of the present invention and incorporated herein by reference as if included herein in their entireties.
As noted in the incorporated references, since the head suspensions are typically formed of relatively weak material, and, since the attachment of the head suspensions to the actuator assembly must be very strong and rigid, the head suspension assemblies typically include mounting plates, contiguous to the mounting portions of the head suspensions, to stiffen the mounting portions and allow for strong mechanical connection of the head suspension to the actuator assembly. These mounting plates are commonly formed of stainless steel having a thickness of approximately 0.008 inches.
Several different attachment systems have historically been used to connect the head suspensions with mounting plates to actuator arms, including rivets (U.S. Pat. No. 4,783,710, to Salyer, et al.), machine screws, adhesives and swaging (U.S. Pat. No. 5,262,911, to Eckerd, et al.). The two immediately preceding noted patents are also assigned to the assignee of the present invention and are also incorporated herein by reference. Each of these prior art head suspension mounting systems has its own particular drawbacks, including limitations on interdisc spacing (machine screws), contamination of assembly fixtures (adhesives), additional component costs (screws, swaging) and convenience of rework (rivets, swaging).
U.S. Pat. No. 5,731,932, issued Mar. 24, 1998, to Crane, et al., also assigned to the assignee of the present invention and incorporated herein by reference, discloses a system for mounting head suspensions that includes the use of a transverse hole and slot arrangement in the distal ends of head mounting arms of actuator assemblies, and cooperatively formed head suspension mounting portions. The teaching of the ""932 reference overcomes many of the drawbacks of the prior art head suspension mounting systems, and also reduces the amount of moving mass in the actuator, by excluding the mass of the previously mentioned mounting plates. It has been found, however, that the head suspension mounting system of the ""932 reference also includes limitations in implementation. In particular, dimensional tolerance variation in the mounting features of the actuator head mounting arms and the thickness of the head suspension materials can lead to either excessive stresses in the materials of the actuator head mounting arms or reduced mounting strength.
The present invention is an improvement on the head suspension mounting system of the ""932 reference, that combines the advantages noted therefor with elimination of the disadvantages noted.
The present invention is a system for mounting head suspensions to actuator head mounting arms in a disc drive. The mounting system includes transverse features in the distal ends of the actuator head mounting arms that cooperate with appropriately formed mounting features welded to or cooperative with the head suspensions. To minimize the effects of dimensional tolerance extremes, the head suspension mounting system includes horizontal slots in the actuator head mounting arms, extending from the transverse features at the distal ends of the actuator head mounting arms back toward the actuator pivot, which serve to vertically divide each actuator head mounting arm into a pair of cooperative cantilever beams, or spring elements. Various embodiments of the transverse features and cooperative mounting features on the head suspension, as well as variations for mounting single head suspensions at the top and bottom of an array of head suspensions, are disclosed.
The features, benefits and advantages of the present invention can best be understood from a review of the following DETAILED DESCRIPTION OF THE INVENTION, when read in conjunction with an examination of the accompanying drawings.